Security Engineering. Ross Anderson

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      Spamming arrived on a small scale when the Internet opened to the public in the mid-1990s, and by 2000 we saw the Earthlink spammer making millions from sending phishing lures. By 2010 spam was costing the world's ISPs and tech companies about $1bn a year in countermeasures, but it earned its operators perhaps one percent of that. The main beneficiaries may have been webmail services such as Yahoo, Hotmail and Gmail, which can operate better spam filters because of scale; during the 2010s, hundreds of millions of people switched to using their services.

      Spam is now a highly specialised business, as getting past modern spam filters requires a whole toolbox of constantly-changing tricks. If you want to use spam to install ransomware, you're better off paying an existing service than trying to learn it all from scratch. Some spam involves industrial-scale email compromise, which can be expensive for the victim; some $350m was knocked off the $4.8bn price at which Yahoo was sold to Verizon after a bulk compromise [772].

2.3.1.4 Bulk account compromise

Some botnets are constantly trying to break into email and other online accounts by trying to guess passwords and password recovery questions. A large email service provider might be recovering several tens of thousands of accounts every day. There are peaks, typically when hackers compromise millions of email addresses and passwords at one website and then try them out at all the others. In 2019, this credential stuffing still accounts for the largest number of attempted account compromises by volume [1885]. Compromised accounts are sold on to people who exploit them in various ways. Primary email accounts often have recovery information for other accounts, including bank accounts if the attacker is lucky. They can also be used for scams such as the stranded traveler, where the victim emails all their friends saying they've been robbed in some foreign city and asking for urgent financial help to pay the hotel bill. If all else fails, compromised email accounts can be used to send spam.

      A variant on the theme is the pay-per-install service, which implants malware on phones or PCs to order and at scale. This can involve a range of phishing lures in a variety of contexts, from free porn sites that ask you to install a special viewer, to sports paraphernalia offers and news about topical events. It can also use more technical means such as drive-by downloads. Such services are often offered by botnets which need them to maintain their own numbers; they might charge third party customers $10-15 per thousand machines infected in the USA and Europe, and perhaps $3 for Asia.

       2.3.1.5 Targeted attackers

      We've seen the emergence of hack-for-hire operators who will try to compromise a specific target account for a fee, of typically $750 [1885]. They will investigate the target, make multiple spear-phishing attempts, try password recovery procedures, and see if they can break in through related accounts. This continues a tradition of private eyes who traditionally helped in divorce cases and also stalked celebrities on behalf of red-top newspapers – though with even fewer ethical constraints now that services can be purchased anonymously online. John Scott-Railton and colleagues exposed the workings of Dark Basin, a hack-for-hire company that had targeted critics of ExxonMobil, and also net neutrality advocates, and traced it to a company in India [1695].

      In recent years, targeted attacks have also been used at scale against small business owners and the finance staff of larger firms in order to carry out various kinds of payment fraud, as I'll discuss below in 2.3.2.

       2.3.1.6 Cashout gangs

      Back in the twentieth century, people who stole credit card numbers would have to go to the trouble of shopping for goods and then selling them to get money out. Nowadays there are specialists who buy compromised bank credentials on underground markets and exploit them. The prices reveal where the real value lies in the criminal chain; a combination of credit card number and expiry date sells for under a dollar, and to get into the single dollars you need a CVV, the cardholder's name and address, and more.

      Cashout techniques change every few years, as paths are discovered through the world's money-laundering controls, and the regulations get tweaked to block them. Some cashout firms organise armies of mules to whom they transfer some of the risk. Back in the mid-2000s, mules could be drug users who would go to stores and buy goods with stolen credit cards; then there was a period when unwitting mules were recruited by ads promising large earnings to ‘agents’ to represent foreign companies but who were used to remit stolen funds through their personal bank accounts. The laundrymen next used Russian banks in Latvia, to which Russian mules would turn up to withdraw cash. Then Liberty Reserve, an unlicensed digital currency based in Costa Rica, was all the rage until it was closed down and its founder arrested in 2013. Bitcoin took over for a while but its popularity with the cybercrime community tailed off as its price became more volatile, as the US Department of the Treasury started arm-twisting bitcoin exchanges into identifying their customers.

      As with spam, cashout is a constantly evolving attack-defence game. We monitor it and analyse the trends using CrimeBB, a database we've assembled of tens of millions of posts in underground hacker forums where cybercriminals buy and sell services including cashout [1501]. It also appears to favour gangs who can scale up, until they get big enough to attract serious law-enforcement attention: in 2020, one Sergey Medvedev pleaded guilty to inflicting more than $568 million in actual losses over the period 2010–15 [1932].

       2.3.1.7 Ransomware

      One reason for the decline in cryptocurrency may have been the growth of ransomware, and as the gangs involved in this switched to payment methods that are easier for victims to use. By 2016–17, 42% of ransomware encountered by US victims demanded prepaid vouchers such as Amazon gift cards; 14% demanded wire transfers and only 12% demanded cryptocurrency; a lot of the low-end ransomware aimed at consumers is now really scareware as it doesn't actually encrypt files at all [1746]. Since 2017, we've seen ransomware-as-a-service platforms; the operators who use these platforms are often amateurs and can't decrypt even if you're willing to pay.

      Meanwhile a number of more professional gangs penetrate systems, install ransomware, wait until several days or weeks of backup data have been encrypted and demand substantial sums of bitcoin. This has grown rapidly over 2019–20, with the most high-profile ransomware victims in the USA being public-sector bodies; several hundred local government bodies and a handful of hospitals have suffered service failures [356]. During the pandemic, more hospitals have been targeted; the medical school at UCSF paid over $1m [1482]. It's an international phenomenon, though, and many private-sector firms fall victim too. Ransomware operators have also been threatening large-scale leaks of personal data to bully victims into paying.

2.3.2 Attacks on banking and payment systems

Attacks on card payment systems started with lost and stolen cards, with forgery at scale arriving in the 1980s; the dotcom boom ramped things up further in the 1990s as many businesses started selling online with little idea of how to detect fraud; and it was card fraud that spawned underground markets in the mid-2000s as criminals sought ways to buy and sell stolen card numbers as well as related equipment and services.

      Another significant component is pre-issue fraud, known in the USA as ‘identity theft’ [670], where criminals obtain credit cards, loans and other assets in your name and leave you to sort out the mess. I write ‘identity theft’ in quotes as it's really just the old-fashioned offence of impersonation. Back in the twentieth century, if someone went to a bank, pretended to be me, borrowed money from them and vanished, then that was the bank's problem, not mine. СКАЧАТЬ